Writing

ABSTRACT

Impermanent marks, they may disappear in a day or less, are created by &#39;&#39;&#39;&#39;writing,&#39;&#39;&#39;&#39; with a stylus presenting an alkanolamine, on a sheet of paper coated with a material which changes to a distinctive color upon exposure to the amine. The marks disappear in a short period of time so that exercise books used at the elementary school level can be reused in the following semester or term without additional cost as would be entailed in the purchase of new books.

United States Patent Inventors Raymond E. Spokes;

John William Edwards, Jr.; Daniel Ward Edwards, all of Ann Arbor, Mich.

June 17, 1969 Nov. 2, 1971 Chem-Rite Associates Ann Arbor, Mich.

Continuation-impart of application Ser. No. 784,091, Dec. 16, 1968, nowabandoned.

Appl. No. Filed Patented Assignee WRITING 4 Claims, 3 Drawing Figs.

US. Cl 1l7/l.7, 117/36.2, 1 17/157, 35/66 Int. Cl B441 l/10 Field ofSearch 1l7/36.2, 0.5, 1, 1.5, 1.7;346/21, 1 1 1; 252/408; 35/61, 66;23/253 TP; 283/6 coai'in orthocresolplztlmlein.

[56] References Cited UNITED STATES PATENTS 456,047 7/1891 Meyer ll7/1.7

997,513 7/1911 Schmidt 117/1 2,631,918 3/1953 Kozak 1 17/362 2,677,7285/1954 Kolb ll7/36.7 2,770,534 l1/1956 Marx 1l7/36.2 2,826,511 3/1958Messinger 117/1 Primary Examiner-Murray Katz Anorney- Kinzer, Dorn andZickert ABSTRACT: lmpermanent marks, they may disappear in a day orless, are created by "writing," with a stylus presenting analkanolamine, on a sheet of paper coated with a material which changesto a distinctive color upon exposure to the amine. The marks disappearin a short period of time so that exercise books used at the elementaryschool level can be reused in the following semester or term withoutadditional cost as would be entailed'in the purchase of new books.

on allcanolamine (e.5.ethanolamine) Con'l'qinin Paper conjunction of theamine and phihalein produces a blue image which disappears after timelapse.

7 systems, and in particular exercises for learning the alphabet andacquiring readingskills, also has other and quite different fields ofutility. where imperrnanent marks (disappearing after a lapse of time)aredesirable, as in the instance of crossword puzzles, temporarytabulations, brief reckonings, and the like.

Workbooks, such as those used in school exercises, are deemedexpendable. Amongthesespecifically is a language system involving a newprogramming techniquerequiring an increase in the total number of booksand in their size as well. In this system, in one manifest form,relatively thick, softbacked books are presented for sight learningrather. than rote memorization- While the system itself takesdifferentforms, attention is directed to FIGS. 1 and 2 which are twoexamples of what can be viewed as text matter inthebooksrln FIG. 1, thestudent is to circle, or otherwise encompass with a mark, the alphabetletters to the right which he recognizes as being identical to the firstone in the left surrounded'by a printed rectangle itself part of thetext. In the system as it is now practiced, such marking by the studentis more or less permanent, the delineation being made by asoft pencil,crayon, or the like. While obviously suchdelineation accomplishes theexercise and enables the teacher to score the work, reuseitnot practicalunless time is taken toerase the completed exercise, but even so theerasures are not necessarily effective.

Other methods have involved use of a colorless plastic sheet placed overthe work, and marks made on the sheet are subsequently removed.

Another example of the visual tracking system is represented by FIG. 2where the classroom exercisefor the student, in the paragraph ofjibberish presented, is to inscribe a mark over the first letter "a" hefinds, is to mark off the first b" he finds, and so on, through theparagraph. The student is to give thesame treatment to all subsequentparagraphs.

It is to be emphasized that the visual tracking system itself isadmittedly satisfactory, but experience has shown that the books reallycannot be reused which has curtailed its adoption except in the moreaffluent school districts where newsets of books can be repeatedlypurchased with regard to successive school terms or semesters.Contributions from federal agencies and other public allocations, nowbeing directed to such educational systems, could be diverted to otherprograms provided the work books could be reused in some efficientmanner.

It is therefore a primary object of the present invention to enable thevisual tracking system to be reduced in cost by the ability to reuse thetexts in a practical sense, and to attain this desirable end by makingit possible to develop a temporary but nonetheless visible mark on paperwhich will become colorless after a lapse of time but within which theteacher can score the exercises.

A related object of the invention is to enable the foregoing objects tobe achieved by so coating a sheet of paper as to present on the writingsurface a small amount of either orthocresolphthalein, thymolphthalein,phenolphthalein or other material which will change color; then when astylus, presenting an alkanolamine or some other volatile base isapplied to the paper, a reaction takes place producing a visible markthat slowly disappears through timefThe mark itself, as thus developedwhen using orthocresolphthalein, is violet in color, being chemicallybasic, but being presented as a mark on paper, which is slightly acid,eventually becomes colorless, but no so rapidly as to precludedistinguishing the marks within a reasonable time period, say, from afew hours to several days. The actual time lapse for invisibility,however, may be easily varied.

While utility in this instance is explained primarily in terms of aneducational system, the invention of course may be practiced under manydifferent circumstances.

Other and further objects of the present invention will be apparent fromthe following description and claims and are illustrated in theaccompanying drawings which, by way of illustration, shows a preferredembodiment of the present invention and the principles thereof and whatis now considered to be the best mode contemplated for applying thoseprinciples. Other embodiments of the invention embodying the same orequivalent principles may be used and structural changes may be made asdesired by those skilled in the art without departing from the presentinvention. In the drawings:

FIGS. 1 and 2 are fragments of text"; and

FIG. 3 shows one mode of practicing the present invention.

There are many chemicals, such as organic dyes, which can by one meansor another he made to change color. or become colorless (or vice versa).Usually this is a bright light phenomenon, or one of oxidation as by ableaching agent. Whatever its form, it must be heated or treatedchemically to develop color.

We have found that by coating a paper sheet with a phthalein, and thenpresenting avolatile alkaline liquid, such asmonoethanolamine-to thecoated sheet, a blue or violet color of extremely good intensity andmarking ability results, capable of disappearing as the result of a merelapse of time and no more. Substantially equal results'are obtained whenusing orthocresolphthalein, thymolphthalein or phenolphthalein. Byemploying two difierent alkanolamines, we are able to arrive at a fluidpossessing the desired vapor pressure after application to the coatedpaper bearing the phthalein from which the transitory color is to bedeveloped, such that at once it will effectively penetrate the coatingand evaporate rapidly enough to avoid smears, will not bleed through thepaper, will not produce a fuzzy image, will disappear at a controlledrate, and may be easily borne by any selected stylus, even a stick. infact, we can easily vary the rate of disappearance of the mark byadjusting the ratio of the one, monoethanolamine, to the ratio of theother which is diethanolamine or any other suitable alkanolamine such asnpropyl amine.

'The coating containing an active component may be applied to any gradeof paper intended as one which'will accept printing ink, but we preferto use a good rosin size paper in which the rosin size content is fromii to 1% percent by weight, itself having a mineral filler content of 3to 12 percent. Such sizes, their composition and their application tothe paper material, are well known in the art, and are not part of thepresent invention. Thus, in practicing the present invention, thecoating material containing an active component characteristic of thepresent invention is applied to a sheet of paper, an in commercialproduction this will be done by means of a doctor blade, or by resortingto a typical rollercoating operation. in a more limited sense, theinvention may be practiced by just swabbing the sheet with a coatingcomposition which presents one of the active components.

EXAMPLE 1 Dissolve 3 grams by weight of orthocresolphthalein in l50 cc.isopropyl alcohol, and add cc. of water for dilution, thus making a 1percent solution of the active component. To this l percent solution add25 cc. of a 4 percent 15,000 c.p.s. Methocel, which is only a thickener,and of which there are many equivalents on the market, including otherforms of methylcellulose, ethylcellulose, carboxymethylcellulose, and soon. The thickener is for the purpose of giving body to the coatingcomposition so that it will have some adhesive characteristics and willstick to and adhere to that side of the paper sheet where the visiblemark is to be made, without flowing or bleeding excessively from or intothe paper base. Thus, one could coat the paper sheet with only thealcohol solution of the active component, but this solution is so thinas to result in a great loss of the active component deep within theinterstices of the paper due to excessive penetration.

EXAMPLE 2 The procedure is the same as in example 1 except that a 2percent solution of the active component is made; but it may be notedthat in actual practice we may use as little as A percent of the activecomponent or a percent solution. The exact amount may thus varydepending upon the intensity of the color wanted. Furthermore, theamount that is spread on the sheet may vary, and this will affectprimarily the extent to which the sheet may be used in repeatedoperations.

EXAMPLE 3 lnstead of orthocresolphthalein, either phenolphthalein orthymolphthalein may be substituted in example 1 or example 2 The aminepresented by the stylus, at the time of contacting the coated side ofthe sheet, FIG. 3, is responsible for developing the blue-to-violetcolor characteristic of the chemical transformation of the other activecomponent, which is the phthalein.

The preferred organic base, ethanolamine, may be a (3:1) mixture of 450cc. of monocthanolamine and 150 cc. of diethanolamine at roomtemperature, but it may also be a mixture of (5:3 375 cc. ofmonocthanolamine and 225 cc. of diethanolamine at room temperature. Theetbanolamine may be either one of these amines by itself, and the ratioor percentage of one compared to the other only determines the rate ofdisappearance of the mark once made on the sheet. Thus, color willdisappear more rapidly with an increase in the amount ofmonocthanolamine which has a vapor pressure at room temperature 100times higher than diethanolamine-l vs. 0.01 mm. (Hg).

The second active component, the ethanolamine. is selected primarily forits effectiveness, availability and low cost, so that there may be achoice of some other organic base as an equivalent which will producethe desired color change and then by evaporation allow the phthalein torestore to its original state bereft of the induced color change.

Thus it will be seen that under the present invention we achieve ourobjectives by incorporating in paper particles of one component (aphthalein) which will change color (and slowly disappear) when exposedto another component presented by a suitable stylus, the other componentpreferably being an alkanolamine.

We claim:

1. A method of developing information on paper comprising: coating paperunifonnly with particles of a first active component selected from thegroup consisting of phenolphthalein, orthocresolphthalein andthymolphthalein, and subsequently delineating said coating intelligentlywith a stylus presenting a second active component which is analkanolamine, thereby to produce a chemical reaction between the twocomponents resulting in a visible mark which without more eventuallydisappears,

2. A method according to claim I in which the amine is a mixture ofmonocthanolamine and diethanolamine.

3. A method according to claim 1 in which the paper is represented bythe pages of a grade school workbook.

4. A method according to claim 2, in which the paper is represented bythe pages of a grade school workbook.

II i II t i

2. A method according to claim 1 in which the amine is a mixture ofmonoethanolamine and diethanolamine.
 3. A method according to claim 1 inwhich the paper is represented by the pages of a grade school workbook.4. A method according to claim 2, in which the paper is represented bythe pages of a grade school workbook.